Described below is a separating device, for separating magnetic or magnetizable particles present in a suspension, having a separating channel through which the suspension can flow, a ferromagnetic yoke arranged on one side of the separating channel, and a separating element arranged at the outlet of the separating channel for separating the magnetic or magnetizable particles. A plurality of coils are arranged along the separating channel that can be controlled by a control device.
A separating device of this kind is known from DE 10 2008 047 852 A1. This separating device is used for a continuous method for separating a mixture of both magnetizable and non-magnetizable particles. With this separating device, it is provided that a magnetic deflecting field, which is variable in terms of time, is generated by the coils, in particular a travelling wave so that the particles accumulate under the influence of the magnetic field or the magnetic field gradient on an inner surface of the separating channel. While a current flows through the separating channel, the magnetizable particles accumulate on the wall of the separating channel so that they can be separated on leaving the separating channel. In contrast to a constant magnetic field, a traveling field which is variable in terms of time is provided so that field-free regions exist in which there is no magnetic field gradient. These field gaps travel with the flow so that, on encountering a field gap, a magnetic or magnetizable particle is released again from the wall of the separating channel and is transported further by the flow. This ensures that there is no excessive build-up of particles, which would have to be removed by a discontinuous method or a corresponding procedural step.
Separating devices can be used to separate a mixture or a suspension of magnetizable and non-magnetizable particles. Here, use is made of a traveling field, which moves along a separating channel in the direction of a separating baffle. This traveling field exerts a force on the magnetic particles, which is directed both toward the wall and perpendicularly thereto, in the direction of flow of the suspension. The combination of this force with the hydrodynamic force of the flowing suspension causes the magnetic particles to be concentrated in the vicinity of the wall of the separating channel and transported in the direction of a separating baffle. The energization of the coils arranged in series along the separating channel takes place such that, at a particular time in neighboring coils the current flows in the same direction, neighboring coils only differ with respect to their phase angle. In the longitudinal direction of the coil arrangement, the current varies in the form of sinusoidal half-waves, which alternate with field-free regions or time segments.
Investigations with the separating device known from DE 10 2008 047 852 A1 revealed that unwanted force components occur in partial regions of the separating channel, the components causing the particles to be moved away from the wall of the separating channel through which the flow passes so that subsequently a certain proportion of the particles could not be separated.